Unrecognized commands are silently ignored in batch mode.  This can be a serious
problem.  For example, great confusion was caused for a time in our
collaboration by someone using /klscint/reemmission/off instead of
/klscint/reemission/off in a batch file.  (Note number of "m"'s.)  The potential
for confusion is real, especially since some built-in Geant4 commands are
themselves misspellings or malapropisms ("/process/inactivate" comes to mind).

The problem arises because G4batch does not check the return value from
UImanager->ApplyCommand(commandLine), while UImanager itself takes no
responsibility for reporting errors to the user, apparently by design (old code
to report "Command Not Found" is explicitly commented out at line 244 of
G4UImanager.cc).